Optical imaging apparatus, optical inspection apparatus, and optical inspection method

ABSTRACT

According to one embodiment, an optical imaging apparatus includes: an image-forming optical portion, a wavelength selection portion, and an imaging portion. The image-forming optical portion forms an image of an object by means of light beams that include a first wavelength and a second wavelength different from the first wavelength. The first wavelength selection portion has wavelength selection regions. The wavelength selection regions are an anisotropic wavelength selection opening having a different distribution of the wavelength selection regions depending on a direction along a first axis and a direction along a second axis. The imaging portion is configured to simultaneously acquire an image of the first light beam and the second light beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2020-186030, filed Nov. 6, 2020, theentire contents of all of which are incorporated herein by reference.

FIELD

Embodiments of the present invention relate to an optical imagingapparatus, an optical inspection apparatus, and an optical inspectionmethod.

BACKGROUND

In various industries, non-contact object surface measurement has becomeimportant. As a conventional method, a technique has been known thatseparates light beams into spectra and illuminates an object with thelight beams, acquires images separated into spectra with an imagingelement, and estimates each light beam direction to acquire informationabout the object surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view that illustrates an opticalinspection apparatus according to a first embodiment;

FIG. 2 is a block diagram of the optical inspection apparatus accordingto the first embodiment;

FIG. 3 is a schematic view of the optical inspection apparatus accordingto the first embodiment along a first plane;

FIG. 4 is a schematic view of the optical inspection apparatus accordingto the first embodiment along a second plane;

FIG. 5 is a schematic perspective view that illustrates an opticalinspection apparatus according to the first embodiment;

FIG. 6 is a schematic perspective view that illustrates an opticalinspection apparatus according to a second embodiment;

FIG. 7 is a schematic perspective view that illustrates an opticalinspection apparatus according to a modification of the secondembodiment;

FIG. 8 is a schematic perspective view that illustrates an opticalinspection apparatus according to a third embodiment;

FIG. 9 is a schematic perspective view that illustrates an opticalinspection apparatus according to a fourth embodiment;

FIG. 10 is a block diagram of the optical inspection apparatus accordingto the fourth embodiment;

FIG. 11 is a schematic cross-sectional view of an illumination portionof an optical inspection apparatus according to Modification 1 of thefourth embodiment along a first plane; and

FIG. 12 is a schematic cross-sectional view of an illumination portionof an optical inspection apparatus according to Modification 2 of thefourth embodiment along a first plane.

DETAILED DESCRIPTION

According to one embodiment, an optical imaging apparatus includes: animage-forming optical portion, a first wavelength selection portion, andan imaging portion. The image-forming optical portion forms an image ofan object by means of light beams that include a first wavelength and asecond wavelength different from the first wavelength. The image-formingoptical portion defines a first axis that intersects a first opticalaxis of the image-forming optical portion, and defines a second axisthat intersects the first optical axis of the image-forming opticalportion and the first axis. The first wavelength selection portion haswavelength selection regions. The wavelength selection regions are ananisotropic wavelength selection opening having a different distributionof the wavelength selection regions depending on a direction along thefirst axis and a direction along the second axis. A first light beam hasthe first wavelength. The first light beam has object-sidetelecentricity in an axis direction of the first axis of theimage-forming optical portion and has object-side non-telecentricity inan axis direction of the second axis. The second light beam has thesecond wavelength. The second light beam has object-sidenon-telecentricity in the axis direction of the first axis and the axisdirection of the second axis. The first wavelength selection portionsimultaneously allows passing of the first light beam and the secondlight beam. The imaging portion is configured to simultaneously acquirean image of the first light beam and the second light beam.

According to one embodiment, an optical inspection method includes:imaging a first light beam that has a first wavelength and a secondlight beam that has a second wavelength different from the firstwavelength at an imaging portion, by means of an image-forming opticalportion passing through the image-forming optical portion and awavelength selection portion from an object; and simultaneouslyacquiring an image of the first light beam passed through the wavelengthselection portion and an image of the second light beam passed throughthe wavelength selection portion by means of the imaging portion. Thefirst beam has object-side telecentricity in an axis direction of afirst axis that crosses a first optical axis of the image-formingoptical portion and has object-side non-telecentricity in an axisdirection of a second axis that crosses the first optical axis and thefirst axis. The second light beam has object-side non-telecentricity inthe axis direction of the first axis and the axis direction of thesecond axis.

According to one embodiment, an optical inspection method includes:incident of a first light beam having a first wavelength and a secondlight beam having a second wavelength different from the firstwavelength on an object; simultaneously passing the first light beam andthe second light beam through a wavelength selection portion; formingimages of the first light beam and the second light beam that have beenallowed to pass through the wavelength selection portion by means of theimage-forming optical portion; and acquiring the images of the firstlight beam and the second light beam that have been allowed to passthrough the wavelength selection portion by means of an imaging portion.The first light beam has object-side telecentricity in an axis directionof a first axis that crosses a first optical axis of an image-formingoptical portion and has object-side non-telecentricity in an axisdirection of a second axis that crosses the first optical axis and thefirst axis. The second light beam has object-side non-telecentricity inthe axis direction of the first axis and the axis direction of thesecond axis.

An object of the present embodiments is to provide an optical imagingapparatuses 12, an optical inspection apparatuses 10, and an opticalinspection method for acquiring information about an object surface.

Hereinafter, each of embodiments will be described with reference to thedrawings. The drawings are schematic or conceptual ones, and therelationship between the thickness and width of each part, and the ratioin size between parts, etc. do not necessarily agree with the actualones. Further, even when identical parts are depicted, the parts may bedepicted with different dimensions and ratios between the drawings. In adescription of each of the embodiments and each of the drawings, anelement similar to an element that has been described in connection withpreceding drawings is denoted by the same sign, and a detaileddescription of the element is appropriately omitted.

First Embodiment

Hereinafter, an optical inspection apparatus 10 according to a firstembodiment will be described with reference to FIGS. 1 to 5.

FIG. 1 illustrates a schematic perspective view of the opticalinspection apparatus 10 according to the present embodiment.

The optical inspection apparatus 10 according to the present embodimentincludes an optical imaging apparatus 12. The optical imaging apparatus12 includes an image-forming optical portion (image-forming opticalelement) 22 that has a first optical axis L1, a wavelength selectionportion (first wavelength selection portion) 24, and an image sensor(imaging portion) 26. As illustrated in FIG. 2, the optical inspectionapparatus 10 includes a controller 18 that is configured to control theimage sensor 26. The controller 18 controls the optical imagingapparatus 12. A display 9 is connected to the controller 18 so thatimages acquired by the image sensor 26 of the controller 18 can bedisplayed. Note that the controller 18 can adjust the image-formingoptical portion 22 by means of what operates electronically or whatreceives electronic signals and operates mechanically. Alternatively,the controller 18 can adjust the wavelength selection portion 24 bymeans of what switches electronically or what receives electronicsignals and switches mechanically.

The controller 18 is a computer. The controller 18 physically includesmemory, such as random-access memory (RAM) and read-only memory (ROM), aprocessor (operation circuit), such as a central processing unit (CPU),a communication interface, and an information storage, such as a harddisk. As the controller 18, a personal computer, a cloud server, atablet terminal, and the like are exemplified. The controller 18functions by executing programs stored in the memory with the processor.

The controller 18 can acquire images from the image sensor 26. Further,the controller 18 performs adjustments related to acquisition of imagesby controlling an exposure time, a frame rate, and the like. Further,the controller 18 determines a hue of an image imaged by the imagesensor 26. The hue of each pixel of the image sensor 26 can bedetermined, for example, by the pixel value of each pixel.

Light is a type of electromagnetic wave. It is assumed that lightincludes X-rays, ultraviolet rays, visible light, infrared rays, amicrowave, and the like. In the present embodiment, it is assumed thatlight is visible light and has a wavelength within a region, forexample, from 400 nm to 760 nm. Preferably, light is not what is calledsingle-color light that has a narrow wavelength range, but includes anappropriate wavelength range, such as visible light.

The image-forming optical portion 22 illustrated in FIG. 1 is, forexample, an image-forming lens. That is to say, the image-formingoptical portion 22 may be a spherical lens, an aspheric lens, anachromatic lens, a Fresnel lens, or the like. In FIG. 1, animage-forming lens as the image-forming optical portion 22 isschematically depicted as one lens as a representation. However, theimage-forming optical portion 22 may be a lens assembly that includes aplurality of lenses. Alternatively, the image-forming optical portion 22may be a concave mirror or a convex mirror, or a combination of aconcave mirror and a convex mirror. That is to say, the image-formingoptical portion 22 may be any optical element that has a function ofgathering a light beam group emitted from one point of an object as aninspection subject, that is to say an object point, at a conjugate imagepoint.

A fact that a light beam group emitted from an object point is gathered(condensed) at an image point by the image-forming optical portion 22 isreferred to as image formation. Alternatively, the fact is also referredto as a transfer of an object point to an image point (conjugate pointof the object point). It is thought that if an object point isinfinitely distant from the image-forming optical portion 22, asillustrated in FIG. 1, a light beam group that has been emitted from anobject point and reaches the image-forming optical portion 22 becomes aparallel-light light beam group. Further, a plane where conjugate pointsto which a parallel-light light beam group from infinity is transferredby the image-forming optical portion 22 gather is referred to as a focalplane of the image-forming optical portion 22. At this time, a conjugateimage point of an object point transferred by the light beams isreferred to as a focus. It is assumed that among the light beam group, apath of a light beam that is vertically incident on the focal plane isthe first optical axis L1 of the image-forming optical portion 22. It isassumed that an optical axis of the image-forming optical portion 22 isa straight line that passes through the center of the image-formingoptical portion 22, and the optical axis of the image-forming opticalportion 22 is the first optical axis L1.

The wavelength selection portion 24 is disposed between theimage-forming optical portion 22 and the image sensor 26. The wavelengthselection portion 24 is disposed in the focal plane on the first opticalaxis L1 of the image-forming optical portion 22.

The wavelength selection portion 24 is formed into, for example, arectangular shape in which a direction (a direction parallel to a secondaxis Ay described below) that perpendicularly crosses the first opticalaxis L1 lies in a lengthwise direction of the rectangular shape. In thepresent embodiment, the wavelength selection portion 24 selectivelyallows passing of a first wavelength and a second wavelength differentfrom the first wavelength through the wavelength selection portion 24.The wavelength selection portion 24 has at least two or more wavelengthselection regions 24 a and 24 b. It is assumed that among the at leasttwo or more wavelength selection regions, one of the two wavelengthselection regions 24 a and 24 b is a first wavelength selection region24 a, and the other is a second wavelength selection region 24 b. Thefirst wavelength selection region 24 a and the second wavelengthselection region 24 b are each formed along the lengthwise direction ofthe wavelength selection portion 24. The first wavelength selectionregion 24 a is disposed on the first optical axis L1. The firstwavelength selection region 24 a is adjacent to the second wavelengthselection region 24 b. The first wavelength selection region 24 a andthe second wavelength selection region 24 b of the wavelength selectionportion 24 are formed in translation symmetry with respect to an axisparallel to the second axis Ay.

The first wavelength selection region 24 a allows passing of a lightbeam that has the first wavelength (first light beam) through the firstwavelength selection region 24 a. Here, allowing passing of a light beammeans directing a light beam from an object point to an image point bytransmission or reflection. In the present embodiment, it is assumedthat the first wavelength selection region 24 a allows regular passingof a light beam of the first wavelength through the first wavelengthselection region 24 a by regular transmission. Here, the regular passingmeans passing by the regular transmission or regular reflection. On theother hand, the first wavelength selection region 24 a shields a lightbeam that has the second wavelength (second light beam). Here, theshielding means no allowing passing of a light beam. That is to say, theshielding means no directing a light beam from an object point to animage point. It is assumed that the first wavelength is, for example,blue light of 450 nm. However, a light beam that passes through thefirst wavelength selection region 24 a has not only the firstwavelength, but also an appropriate range of spectrum that includes awavelength of 450 nm.

The second wavelength selection region 24 b allows passing of a lightbeam of the second wavelength through the second wavelength selectionregion 24 b. On the other hand, the second wavelength selection region24 b shields a light beam of the first wavelength. It is assumed thatthe second wavelength is red light of 650 nm. However, a light beam thatpasses through the second wavelength selection region 24 b is not onlythe second wavelength, but also an appropriate range of spectrum thatincludes 650 nm.

The image sensor 26 includes at least one or more pixel. Preferably, theimage sensor 26 includes a plurality of pixels. It is assumed that eachpixel can receive light beams of at least two different wavelengths,that is to say can receive a light beam of the first wavelength and alight beam of the second wavelength. It is assumed that a plane thatincludes a region where the image sensor 26 is disposed is an imageplane of the image-forming optical portion 22. The image sensor 26 maybe an area sensor or a linear sensor. Further, each of the pixels of theimage sensor 26 may include color channels of three channels of red (R),green (G), and blue (B). In the present embodiment, the image sensor 26is an area sensor, and each pixel includes two color channels of red andblue, as illustrated in FIG. 1. That is to say, the image sensor 26 canreceive blue light of a wavelength of 450 nm and red light of awavelength of 650 nm with respective separate color channels.

In the present embodiment, a first axis Ax is set up in such a mannerthat the first axis Ax perpendicularly crosses the first optical axis L1of the image-forming optical portion 22. However, the first axis Ax isnot limited to this, and the first axis Ax may be any direction thatcrosses the first optical axis L1 of the image-forming optical portion22. In the present embodiment, an axis direction of the first axis Axcorresponds to a direction in which the first wavelength selectionregion 24 a and the second wavelength selection region 24 b align. Thatis to say, the first wavelength selection region 24 a and the secondwavelength selection region 24 b are aligned offset in the axisdirection of the first axis Ax. In the present embodiment, the secondaxis Ay is set up in a direction that perpendicularly crosses both thefirst axis Ax and the first optical axis L1. However, the second axis Ayis not limited to this, and the second axis Ay may be any direction thatcrosses both of the first axis Ax and the first optical axis L1. In thepresent embodiment, it is assumed that an axis direction of the secondaxis Ay is along the lengthwise direction of the wavelength selectionportion 24.

It is assumed that a plane where the first axis Ax and the first opticalaxis L1 extend is a first plane (imaginary plane), and a plane where thesecond axis Ay and the first optical axis L1 extend is a second plane(imaginary plane).

FIG. 3 illustrates a cross-sectional view of the optical inspectionapparatus 10 along the first plane. FIG. 4 illustrates a cross-sectionalview of the optical inspection apparatus 10 along the second plane.

As illustrated in FIGS. 1 and 3, it is assumed that among light beamsfrom the object side, light beams that are parallel to the first opticalaxis L1 and within the first plane are a first light beam group 1. As arepresentative of the first light beam group 1, two light beams of afirst light beam 1 a and a first light beam 1 b are considered. It isassumed that among light beams from the object side, light beams thatare in directions that is inclined relative to the first optical axis L1and within the first plane are a second light beam group 2. As arepresentative of the second light beam group 2, two light beams of asecond light beam 2 a and a second light beam 2 b are considered.

As illustrated in FIGS. 1 and 4, it is assumed that among light beamsfrom the object side, light beams that are parallel to the first opticalaxis L1 and within the second plane are a third light beam group. As arepresentative of the third light beam group, a third light beam 3 isconsidered. It is assumed that among light beams from the object side,light beams that are in directions that is inclined relative to thefirst optical axis L1 and within the second plane are a fourth lightbeam group. As a representative of the fourth light beam group, a fourthlight beam 4 is considered.

As illustrated in FIGS. 1 and 3, a plane parallel to the first planesimultaneously crosses the first wavelength selection region 24 a andthe second wavelength selection region 24 b of the wavelength selectionportion 24. That is to say, a plane parallel to the first plane crossesthe at least two different wavelength selection regions 24 a and 24 b ofthe wavelength selection portion 24. As illustrated in FIGS. 1 and 4, aplane parallel to the second plane crosses the one wavelength selectionregion 24 a of the wavelength selection portion 24. That is to say, thenumber of wavelength selection regions of the wavelength selectionportion 24 that the first plane crosses is different from the number ofwavelength selection regions of the wavelength selection portion 24 thatthe second plane crosses. Therefore, the wavelength selection portion 24is non-isotropic or anisotropic, and has anisotropy. In the presentembodiment, such a wavelength selection portion 24 is referred to as ananisotropic wavelength selection opening. That is to say, it is assumedthat the wavelength selection portion 24 that has wavelength selectionregion distributions that differ according to directions of the firstaxis Ax and the second axis Ay is an anisotropic wavelength selectionopening.

In an optical system in which the image-forming optical portion 22 makeslight beams from an object point form an image at an image point, anoptical system that makes main light beams parallel to the first opticalaxis L1 on the object side is generally referred to as an object-sidetelecentric optical system. In the present embodiment, if theimage-forming optical portion 22 makes light beams that aresubstantially parallel to the first optical axis L1 on the object sideform an image, it is defined that the light beams have object-sidetelecentricity. On the other hand, in a case to the contrary, that is tosay if the image-forming optical portion 22 makes light beams that arenot substantially parallel to but inclined relative to the first opticalaxis L1 on the object side form an image, it is defined that the lightbeams have object-side non-telecentricity.

Under the above configuration, an operation principle of the opticalinspection apparatus 10 according to the present embodiment will bedescribed.

The light beams 1 a and 1 b of the first light beam group 1 from theobject side are parallel to the first optical axis L1. The light beams 1a and 1 b reach a focus in a focal plane of the image-forming opticalportion 22. That is to say, the first light beams 1 a and 1 b reach thefocus. Therefore, the first light beams 1 a and 1 b reach the firstwavelength selection region 24 a of the wavelength selection portion 24disposed in the focal plane. That is to say, the first light beams 1 aand 1 b that have telecentricity in the first plane reach the firstwavelength selection region 24 a.

The light beams 2 a and 2 b of the second light beam group 2 from theobject side is inclined relative to the first optical axis L1 in thefirst plane. The light beams 2 a and 2 b of the second light beam group2 are away from the focus in the focal plane of the image-formingoptical portion 22, and reach the second wavelength selection region 24b. That is to say, the second light beams 2 a and 2 b reach the secondwavelength selection region 24 b. That is to say, the light beams 2 aand 2 b that have non-telecentricity in the first plane reach the secondwavelength selection region 24 b.

The light beam 3 of the third light beam group from the object side isparallel to the first optical axis L1 in the second plane. The lightbeam 3 of the third light beam group reaches the focus in the focalplane of the image-forming optical portion 22. Therefore, the thirdlight beam 3 reaches the first wavelength selection region 24 a of thewavelength selection portion 24 disposed in the focal plane. That is tosay, the light beam 3 that has telecentricity in the second planereaches the first wavelength selection region 24 a.

The light beam 4 of the fourth light beam group from the object sideinclines relative to the first optical axis L1 in the second plane. Thelight beam 4 of the fourth light beam group reaches the first wavelengthselection region 24 a that is away from the focus in the focal plane ofthe image-forming optical portion 22. That is to say, the fourth lightbeam 4 reaches the first wavelength selection region 24 a. That is tosay, a light beam that has non-telecentricity in the second planereaches the first wavelength selection region 24 a.

In this way, the light beams 1 a and 1 b that have telecentricity in thefirst plane and the light beams 2 a and 2 b that have non-telecentricityin the first plane reach the respective different wavelength selectionregions. On the other hand, the light beam 3 that has telecentricity inthe second plane and the light beam 4 that has non-telecentricity in thesecond plane both reach the same wavelength selection region 24 a.

With respect to any light beam that reaches the image-forming opticalportion 22 in any direction from the object side, a projection of thepath projected on the first plane (see FIGS. 1 and 3) and a projectionof the path projected on the second plane (see FIGS. 1 and 4) areconsidered. To each of the projected light beams, the characteristicsdescribed above are each similarly satisfied. That is to say, a lightbeam that is projected on the first plane and has telecentricity, and alight beam that is projected on the first plane and hasnon-telecentricity reach different wavelength selection regions of thewavelength selection portion 24. On the other hand, a light beam that isprojected on the second plane and has telecentricity, and a light beamthat is projected on the second plane and has non-telecentricity bothreach the same wavelength selection region 24 a.

Due to what has been described above, the optical imaging apparatus 12of the optical inspection apparatus 10 according to the presentembodiment operates as follows:

If blue light (light beams of the first wavelength) of an object isimaged by the image sensor 26 of the optical inspection apparatus 10according to the present embodiment, the blue light passes through thefirst wavelength selection region 24 a of the wavelength selectionportion 24. At this time, the first wavelength selection region 24 a ofthe wavelength selection portion 24 shields red light (light beams ofthe second wavelength). Blue light has telecentricity in an axisdirection of the first axis Ax. That is to say, the optical inspectionapparatus 10 can acquire a telecentric image of blue light with theimage sensor 26. A telecentric image has an advantage that a telecentricimage does not depend on farness and nearness of an object. Therefore,an actual size of an object can be acquired with respect to an axisdirection of the first axis Ax. On the other hand, blue light hasnon-telecentricity in an axis direction of the second axis Ay. This canbe paraphrased as having entocentricity. That is to say, an entocentricimage can be acquired that has an angle of view that is wide in an axisdirection of the second axis Ay, and has perspectiveness.

If red light of an object is imaged by the image sensor 26 of theoptical inspection apparatus 10, the red light passes through the secondwavelength selection region 24 b of the wavelength selection portion 24.At this time, the second wavelength selection region 24 b of thewavelength selection portion 24 shields blue light. Red light hasnon-telecentricity in both an axis direction of the first axis Ax and anaxis direction of the second axis Ay. This can be paraphrased as havingentocentricity. That is to say, the optical inspection apparatus 10 canacquire an entocentric image of red light with the image sensor 26.Therefore, the optical inspection apparatus 10 can acquire an image thathas a wide angle of view.

In this way, the image sensor 26 of the optical inspection apparatus 10according to the present embodiment simultaneously acquires an image ofblue light (that corresponds to, for example, regular-reflection light)and an image of red light (that corresponds to, for example, scatteredlight), along a direction of the first axis Ax. Then the controller 18determines a hue of an object, based on the images acquired by the imagesensor 26. Here, if there is a foreign matter or minute protrusions andrecesses of scales close to a wavelength of light on a surface of anobject of an inspection subject (that is referred to as an objectsurface), light beams are scattered, and the image sensor 26 acquires animage as red light. Therefore, the optical imaging apparatus 12 of theoptical inspection apparatus 10 according to the present embodiment canbe used to acquire information about an object surface, and inspect theobject surface.

Further, the optical imaging apparatus 12 of the optical inspectionapparatus 10 according to the present embodiment can acquire an image ofblue light with an angle of view that exceeds a lens diameter of theimage-forming optical portion 22 and an image of red light with an angleof view that exceeds a lens diameter of the image-forming opticalportion 22, along a direction of the first axis Ax and a direction ofthe second axis Ay. Therefore, the optical imaging apparatus 12 of theoptical inspection apparatus 10 according to the present embodiment canacquire an image with a large angle of view, while acquiring informationabout an object surface.

An optical inspection method of an object using the optical imagingapparatus 12 of the optical inspection apparatus 10 will be brieflydescribed.

Light beams from an object that include a first wavelength (for example,blue light) and a second wavelength (for example, red light) are made toreach the wavelength selection portion 24 by the image-forming opticalportion 22. The wavelength selection portion 24 selectively allowspassing of a light beam of the first wavelength and a light beam of thesecond wavelength through the wavelength selection portion 24 to formimages at the image sensor 26. The wavelength selection portion 24allows passing of a light beam of the first wavelength through the firstwavelength selection region 24 a of the wavelength selection portion 24,and allows passing of a light beam of the second wavelength through thesecond wavelength selection region 24 b of the wavelength selectionportion 24. The light beam of the first wavelength has object-sidetelecentricity in an axis direction of the first axis Ax that crossesthe first optical axis L1 of the image-forming optical portion 22 andhas object-side non-telecentricity in an axis direction of the secondaxis Ay that crosses the first optical axis L1 and the first axis Ax.The light beam of the second wavelength has object-sidenon-telecentricity in an axis direction of the first axis Ax and theaxis direction of the second axis Ay. At this time, the first wavelengthselection region 24 a shields passing of a light beam of the secondwavelength through the first wavelength selection region 24 a, and thesecond wavelength selection region 24 b shields passing of a light beamof the first wavelength through the second wavelength selection region24 b. Then images of light beams of the first wavelength and the secondwavelength that have passed through the wavelength selection portion 24are simultaneously acquired by the image sensor 26.

In this way, the optical imaging apparatus 12 of the optical inspectionapparatus 10 according to the present embodiment can acquire informationabout an object surface without separating light beams made to beincident on the image-forming optical portion 22, into spectra, on theobject side that is a side opposite the wavelength selection portion 24.

An optical imaging apparatus 12 of an optical inspection apparatus 10illustrated in FIG. 5 has the same structure as the optical imagingapparatus 12 of the optical inspection apparatus 10 illustrated inFIG. 1. As illustrated in FIG. 5, it is assumed that light beams 5 and 6from an object point O are imaged at an image point IP on an imagesensor 26.

Here, it is assumed that among the light beams 5 and 6 from the objectpoint O, a light beam that is incident on an image-forming opticalportion 22 in parallel to a first optical axis L1 in a first plane is afifth light beam 5. Further, it is assumed that a light beam that isincident on the image-forming optical portion 22 while inclined relativeto the first optical axis L1 in the first plane and inclined relative tothe first optical axis L1 in a second plane is a sixth light beam 6.

The fifth light beam 5 reaches a first wavelength selection region 24 a,and a light beam that has a first wavelength passes through the firstwavelength selection region 24 a and reaches the image point IP. That isto say, the fifth light beam 5 is imaged as blue light by the imagesensor 26. The sixth light beam 6 reaches a second wavelength selectionregion 24 b, and a light beam that has a second wavelength passesthrough the second wavelength selection region 24 b and reaches theimage point IP. That is to say, the sixth light beam 6 is imaged as redlight by the image sensor 26. Therefore, a controller 18 can identify alight beam direction that passes through a wavelength selection portion24 from the object point O, based on a color of an image acquired by theimage sensor 26. That is to say, the controller 18 acquires a directionof a light beam relative to a first axis Ax, based on a hue of an imageacquired by the image sensor 26.

Due to what has been described above, the optical imaging apparatus 12of the optical inspection apparatus 10 according to FIG. 5 operates asfollows:

If blue light (light beams of a first wavelength) from an object isimaged by the image sensor 26 of the optical inspection apparatus 10according to the present embodiment, the blue light passes through thefirst wavelength selection region 24 a of the wavelength selectionportion 24. At this time, the first wavelength selection region 24 a ofthe wavelength selection portion 24 shields red light (light beams ofthe second wavelength). Blue light has telecentricity in an axisdirection of the first axis Ax. That is to say, the optical inspectionapparatus 10 can acquire a telecentric image of blue light with theimage sensor 26. A telecentric image has an advantage that a telecentricimage does not depend on farness and nearness of an object O. Therefore,an actual size of an object O can be acquired with respect to an axisdirection of the first axis Ax. On the other hand, blue light hasnon-telecentricity in an axis direction of the second axis Ay. This canbe paraphrased as having entocentricity. That is to say, an entocentricimage can be acquired that has an angle of view that is wide in an axisdirection of the second axis Ay, and has perspectiveness.

If red light (light beams of the second wavelength) from an object isimaged by the image sensor 26 of the optical inspection apparatus 10,the red light passes through the second wavelength selection region 24 bof the wavelength selection portion 24. At this time, the secondwavelength selection region 24 b of the wavelength selection portion 24shields blue light. Red light has non-telecentricity in both an axisdirection of the first axis Ax and an axis direction of the second axisAy. This can be paraphrased as having entocentricity. That is to say,the optical inspection apparatus 10 can acquire an entocentric image ofred light with the image sensor 26. Therefore, the optical inspectionapparatus 10 can acquire an image that has a wide angle of view.

Further, a surface state or a surface shape at an object point O changesa light arrangement distribution of light beams from the object point O.The wavelength selection portion 24 of the optical inspection apparatus10 according to the present embodiment selectively allows passing ofblue light or red light among light beams from an object point O throughthe wavelength selection portion 24, according to directions of thelight beams, and the blue light or the red light is imaged by the imagesensor 26. Therefore, a component ratio of the blue light and the redlight received by pixels of the image sensor 26 changes according to asurface state or a surface shape of the object point O. That is to say,the controller 18 of the optical inspection apparatus 10 performsprocessing that estimates a surface state or a surface shape of theobject point O, based on a hue of an image imaged by the image sensor26.

Due to the above, a telecentric image in an axis direction of the firstaxis Ax and an entocentric image in an axis direction of the second axisAy can be simultaneously acquired by the image sensor 26 of the opticalimaging apparatus 12 of the optical inspection apparatus 10 according tothe present embodiment. Further, the controller 18 of the opticalimaging apparatus 12 can estimate a surface state or a surface shape ofan object, based on a hue of an imaged image.

According to the present embodiment, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

In the present embodiment, a light beam that the first wavelengthselection region 24 a allows passing through the first wavelengthselection region 24 a is blue light, and a light beam that the firstwavelength selection region 24 a shields is red light. A light beam thatthe second wavelength selection region 24 b allows passing through thesecond wavelength selection region 24 b is red light, and a light beamthat the second wavelength selection region 24 b shields is blue light.A light beam that the first wavelength selection region 24 a allowspassing through the first wavelength selection region 24 a may be redlight, and a light beam that the first wavelength selection region 24 ashields may be blue light, and a light beam that the second wavelengthselection region 24 b allows passing through the second wavelengthselection region 24 b may be blue light, and a light beam that thesecond wavelength selection region 24 b shields may be red light.

The first wavelength selection region 24 a may shield all light beams,irrespective of wavelengths. That is to say, the first wavelengthselection region 24 a may shield both a light beam of a first wavelengthand a light beam of a second wavelength. In this case, an image of bluelight (light beam of the first wavelength) is not imaged. On the otherhand, a light beam of red light (light beam of the second wavelength)that has non-telecentricity passes through the second wavelengthselection region 24 b, and is imaged. Therefore, the controller 18 canextract a non-telecentric image by means of the red light (secondwavelength). That is to say, an image in which among light beams from anobject, light beams along the first optical axis L1 are shielded can beacquired. Therefore, if a light beam intensity along the first opticalaxis L1, for example, is strong, and there is a halation in an imagedimage, the halation can be decreased. Further, there is an advantagethat if an object surface is a diffusion surface, and scattered light,with the scattering center being the first optical axis L1 (a lightarrangement distribution is in axis symmetry with respect to the firstoptical axis L1), is incident on the image-forming optical portion 22, alarge scattering angle component can be extracted. Therefore, a surfacestate of an object surface can be estimated.

Note that in the present embodiment, wavelengths of green light areexcluded from the first wavelength selection region 24 a and the secondwavelength selection region 24 b of the two colors of the wavelengthselection portion 24. The reason is that an overlapping portion ofwavelengths of blue light and green light, and an overlapping portion ofwavelengths of green light and red light are larger than an overlappingportion of wavelengths of blue light and red light. In other words, thereason is that wavelengths of green light are between wavelengths ofblue light and wavelengths of red light, and thus sectioning ofwavelengths of blue light and wavelengths of red light is easier thanusing wavelengths of green light. A range of the first wavelength and arange of the second wavelength are not limited to the wavelengthsdescribed above and may be any wavelength if the range of the firstwavelength and the range of the second wavelength are differentwavelengths. Further, it is assumed that spectra of light beams thatpass through different wavelength selection regions of the wavelengthselection portion 24 are different. If the spectra are different, huesare different.

As described below, if each pixel of an image sensor 26 includes colorchannels of, for example, three channels of R, G, and B, and awavelength selection portion 24 includes wavelength selection regions 24a, 24 b, and 24 c that correspond to three wavelengths (see FIG. 8),green light can be acquired in addition to blue light and red light.

In the present embodiment, an example is described in which the imagesensor 26 that includes an appropriate wavelength range, such as bluelight and red light, is used. Using a multispectral camera or ahyperspectral camera as the image sensor 26 allows colors of, forexample, a wavelength region of visible light from 400 nm to 760 nm tobe separated and an image to be acquired for each of appropriatewavelengths (for example, a wavelength of 5 nm in case of ahyperspectral camera). Therefore, using a multispectral camera or ahyperspectral camera as the image sensor 26, as described above, allowsinformation about an object surface to be acquired. In this case, thewavelength selection portion 24 is not only divided into the twowavelength selection regions 24 a and 24 b, but also may be divided intoa plurality of wavelength selection regions.

Second Embodiment

Hereinafter, an optical inspection apparatus according to the presentembodiment will be described with reference to FIG. 6.

FIG. 6 illustrates a schematic perspective view of an optical inspectionapparatus 10 according to the present embodiment. A basic configurationof an optical imaging apparatus 12 of the optical inspection apparatus10 according to the present embodiment is similar to a basicconfiguration of the optical imaging apparatus 12 according to the firstembodiment.

The optical imaging apparatus 12 includes a beam splitter 32, awavelength selection portion (second wavelength selection portion) 124as an anisotropic wavelength selection opening, and an image sensor 126,in addition to the configuration of the first embodiment. The imagesensor 126 is controlled by a controller 18. The image sensor 126 issynchronized by control of the controller 18 so that the image sensor126 and the image sensor 26 simultaneously acquire images.

The beam splitter 32 is disposed on a first optical axis L1 between animage-forming optical portion 22 and a wavelength selection portion 24.It is assumed that the beam splitter 32 is, for example, anon-polarizing beam splitter. However, the beam splitter 32 is notlimited to a non-polarizing beam splitter, and may be a polarizing beamsplitter. The beam splitter 32 may be anything that splits light beams.It is assumed that a light beam that passes through the beam splitter 32has an optical axis L11, and a light beam reflected by the beam splitter32 has an optical axis L12.

The wavelength selection portions 24 and 124 have the sameconfiguration. Therefore, the wavelength selection portions 24 and 124are both anisotropic wavelength selection openings. The wavelengthselection portion 24 is in symmetry (translation symmetry) with respectto an axis parallel to a second axis Ay. The wavelength selectionportion 124 is in symmetry (translation symmetry) with respect to anaxis parallel to a first axis Ax. That is to say, the wavelengthselection portion 24 has a lengthwise direction in a direction along thesecond axis Ay. The wavelength selection portion 124 has a lengthwisedirection in a direction along the first axis Ax. The number thatcrosses wavelength selection regions in a direction along an axisdirection parallel to the first optical axis L1 is different from thenumber that crosses the wavelength selection regions in a directionalong the first axis Ax. Therefore, the wavelength selection portion 124is non-isotropic or anisotropic, and has anisotropy.

The image sensors 26 and 126 have the same configuration. The imagesensor 126 is disposed in parallel to the wavelength selection portion124, that is to say perpendicularly to the optical axis L12.

Under the above configuration, an operation principle of the opticalinspection apparatus 10 according to the present embodiment will bedescribed.

Blue light that passes through the image-forming optical portion 22, thebeam splitter 32, and the wavelength selection portion 24 hastelecentricity in an axis direction of the first axis Ax. That is tosay, a telecentric image can be acquired due to blue light. Atelecentric image has an advantage that a telecentric image does notdepend on farness and nearness of an object. Therefore, an actual sizecan be acquired with respect to an axis direction of the first axis Ax.On the other hand, blue light has non-telecentricity in an axisdirection of the second axis Ay. This can be paraphrased as havingentocentricity. That is to say, an entocentric image can be acquiredthat has an angle of view that is wide in an axis direction of thesecond axis Ay, and has perspectiveness.

Blue light that passes through the image-forming optical portion 22, issplit by the beam splitter 32, and passes through the wavelengthselection portion 124 has telecentricity in an axis direction of thesecond axis Ay. That is to say, a telecentric image can be acquired dueto blue light. A telecentric image has an advantage that a telecentricimage does not depend on farness and nearness of an object. Therefore,an actual size can be acquired with respect to an axis direction of thesecond axis Ay. On the other hand, blue light has non-telecentricity inan axis direction of the first axis Ax. This can be paraphrased ashaving entocentricity. That is to say, an entocentric image can beacquired that has an angle of view that is wide in an axis direction ofthe first axis Ax, and has perspectiveness.

A combination of the wavelength selection portion 24 that has alengthwise direction in a direction parallel to an axis direction of thesecond axis Ay of the image-forming optical portion 22, and the imagesensor 26, and a combination of the wavelength selection portion 124that has a lengthwise direction in a direction parallel to an axisdirection of the first axis Ax of the image-forming optical portion 22,and the image sensor 126 allow the optical inspection apparatus 10according to the present embodiment to simultaneously acquire both atelecentric image and an entocentric image, in a direction along thefirst axis Ax and in a direction along the second axis Ay, from theobject side. Further, the controller 18 of the optical imaging apparatus12 of the optical inspection apparatus 10 according to the presentembodiment can acquire a light beam direction on the object side, basedon a hue acquired by the image sensors 26 and 126.

According to the present embodiment, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

(First Modification)

FIG. 7 illustrates a schematic perspective view of an optical inspectionapparatus 10 according to a first modification of the presentembodiment.

A basic configuration of an optical imaging apparatus 12 of the opticalinspection apparatus 10 according to the present modification is similarto a basic configuration of the optical imaging apparatus 12 accordingto the second embodiment.

With reference to the configuration of the first embodiment, asdescribed in the second embodiment, the optical imaging apparatus 12according to the present modification includes a beam splitter 32, awavelength selection portion 124, mirrors 34 and 36, a polarizing beamsplitter 38, and an image sensor 226, in addition to the configurationof the first embodiment. The image sensor 226 is controlled by acontroller 18.

The beam splitter 32 according to the present modification is disposedon a first optical axis L1 between an image-forming optical portion 22and a wavelength selection portion 24. The wavelength selection portion24 is disposed between the mirror 34 and the polarizing beam splitter32. The wavelength selection portion 124 is disposed between the mirror36 and the polarizing beam splitter 32. The polarizing beam splitter 38is disposed on light paths of light reflected by the mirrors 34 and 36.

The beam splitter 32 is a polarizing beam splitter, and splits, forexample, polarized-light components that are orthogonal to each other.Further, the image sensor 226 is a polarized-light image sensor, andidentifies and receives two polarized-light components that areorthogonal to each other, at each pixel.

One polarized light component (first polarized-light component) of twopolarized-light components split by the polarizing beam splitter 32 ismade to be incident on the wavelength selection portion 24 on an opticalaxis L11. The other polarized light component (a second polarized-lightcomponent different from the first polarized-light component) is made tobe incident on the wavelength selection portion 124 on an optical axisL12.

The mirror 34 directs light beams that has passed through the wavelengthselection portion 24 (light of a predetermined polarized-lightcomponent) to the another polarizing beam splitter 38. The mirror 36directs light beams that has passed through the wavelength selectionportion 124 (light of a polarized-light component different from thepredetermined polarized-light component) to the another polarizing beamsplitter 38. The another polarizing beam splitter 38 multiplexes thepolarized-light components of the two light beams. Therefore, the twomultiplexed light beams become light beams that have the same opticalaxis, and are made to be incident on the polarized-light image sensor226.

While the polarized-light image sensor 226 is controlled by thecontroller 18, the polarized-light image sensor 226 identifies andreceives two polarized-light components that are orthogonal to eachother, at each pixel.

Due to the above, both a telecentric image and an entocentric image,from the object side, in a direction along a first axis Ax and in adirection along a second axis Ay, can be simultaneously acquired by theone polarized-light image sensor 226. Further, the controller 18 of theoptical imaging apparatus 12 of the optical inspection apparatus 10according to the present embodiment can acquire a light beam directionon the object side, based on a hue acquired by the image sensors 26 and126.

According to the present modification, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

Third Embodiment

Hereinafter, an optical inspection apparatus according to the presentembodiment will be described with reference to FIG. 8.

FIG. 8 illustrates a schematic perspective view of an optical inspectionapparatus 10 according to the present embodiment. A basic configurationof an optical imaging apparatus 12 of the optical inspection apparatus10 according to the present embodiment is similar to a basicconfiguration of the optical imaging apparatus 12 according to the firstembodiment.

In the present embodiment, a wavelength selection portion 24 is disposedcloser to an object as an inspection subject than an image-formingoptical portion 22 is disposed. The wavelength selection portion 24 isdisposed on a first optical axis L1 of the image-forming optical portion22. A first mirror 42 is disposed closer to the object than theimage-forming optical portion 22 and the wavelength selection portion 24are disposed. A second mirror 44 is disposed between the image-formingoptical portion 22 and an image sensor 26. A normal-line direction of areflection surface of the first mirror 42 is parallel to a first axisAx. A normal-line direction of a reflection surface of the second mirror44 is parallel to the first axis Ax.

The number of wavelength selection regions of the wavelength selectionportion 24 that a first plane crosses is different from the number ofwavelength selection regions of the wavelength selection portion 24 thata second plane crosses. Therefore, the wavelength selection portion 24is non-isotropic or anisotropic, and has anisotropy. Therefore, thewavelength selection portion 24 is an anisotropic wavelength selectionopening. In the present embodiment, the wavelength selection portion 24has a lengthwise direction along a second axis Ay, and is divided intoat least three different regions along a direction along the first axisAx. In the present embodiment, the wavelength selection portion 24includes three different wavelength selection regions 24 a, 24 b, and 24c. The three different wavelength selection regions 24 a, 24 b, and 24 care a first wavelength selection region 24 a, a second wavelengthselection region 24 b, and a third wavelength selection region 24 c. Inthe present embodiment, the first wavelength selection region 24 aallows passing of blue light through the first wavelength selectionregion 24 a, and shields green light and red light. The secondwavelength selection region 24 b allows passing of red light through thesecond wavelength selection region 24 b, and shields blue light andgreen light. The third wavelength selection region 24 c allows passingof green light through the third wavelength selection region 24 c, andshields red light and blue light. Note that here, it is assumed that thefirst wavelength selection region 24 a, for example, is disposed on thefirst optical axis L1 of the image-forming optical portion 22.

The image sensor 26 is a linear sensor. It is assumed that a light beamfrom an object is a seventh light beam 7. The seventh light beam 7 froman object is reflected by the first mirror 42, and is made to beincident on the image sensor 26 through the wavelength selection region24 a, 24 b, or 24 c of the wavelength selection portion 24, theimage-forming optical portion 22, and the second mirror 44.

In the first plane where the first axis Ax and the first optical axis L1extend, the image sensor 26 can be considered as a point. In the presentembodiment, in the first plane, an image of an only one region (only oneobject point) of an object that can be considered as substantially apoint is image formed at the linear sensor 26. In this case, it can besaid that in the first plane, blue light that is incident on thewavelength selection portion 24 from an only one object point and passesthrough the wavelength selection region 24 a, red light that is incidenton the wavelength selection portion 24 from the only one object pointand passes through the wavelength selection region 24 b, and green lightthat is incident on the wavelength selection portion 24 from the onlyone object point and passes through the wavelength selection region 24 chave different directions. That is to say, if the image sensor 26 is alinear sensor, a light beam direction can be identified by thecontroller 18, based on a hue in the first plane, even if the wavelengthselection regions 24 a, 24 b, and 24 c are disposed closer to the objectthan the image-forming optical portion 22 is disposed.

Light beams that do not directly reach the image-forming optical portion22 from an object point are indirectly directed to the linear sensor 26by the first mirror 42 and the second mirror 44. Therefore, the opticalimaging apparatus 12 of the optical inspection apparatus 10 according tothe present embodiment can identify directions of light beams of a widerange.

In this way, the optical imaging apparatus 12 of the optical inspectionapparatus 10 according to the present embodiment can acquire informationabout an object surface.

An optical inspection method of an object using the optical imagingapparatus 12 of the optical inspection apparatus 10 will be brieflydescribed.

Light beams that include a first wavelength (for example, blue light)and a second wavelength (for example, red light) are made to be incidenton an object. At this time, a light beam of the first wavelength isallowed to pass through the first wavelength selection region 24 a ofthe wavelength selection portion 24, and simultaneously a light beam ofthe second wavelength is allowed to pass through the first wavelengthselection region 24 a of the wavelength selection portion 24, andsimultaneously a light beam of the second wavelength. The light beam ofthe first wavelength has object-side telecentricity in an axis directionof the first axis Ax that crosses the first optical axis L1 of theimage-forming optical portion 22 and has object-side non-telecentricityin an axis direction of the second axis Ay that crosses the firstoptical axis L1 and the first axis Ax. The light beam of the secondwavelength has object-side non-telecentricity in an axis direction ofthe first axis Ax and the axis direction of the second axis Ay. Then theimage-forming optical portion 22 makes the light beams of the firstwavelength and the second wavelength that have passed through thewavelength selection portion 24 form images, and the images of the lightbeams of the first wavelength and the second wavelength aresimultaneously acquired by the image sensor 26.

In this way, according to the present embodiment, the optical imagingapparatus 12, the optical inspection apparatus 10, and the opticalinspection method for acquiring information about an object surface canbe provided.

Fourth Embodiment

Hereinafter, an optical inspection apparatus 10 according to the presentembodiment will be described with reference to FIGS. 9 and 10.

FIG. 9 illustrates a schematic perspective view of the opticalinspection apparatus 10 according to the present embodiment. FIG. 10illustrates a block diagram of the optical inspection apparatus 10.

As illustrated in FIG. 9, the optical inspection apparatus 10 accordingto the present embodiment includes an optical imaging apparatus 12, anillumination portion 14, and a conveyance portion 16. For example,positions of the optical imaging apparatus 12 and the illuminationportion 14 are fixed to a floor surface (not illustrated), and aconveyance path 16 a of the conveyance portion 16 moves relative to theoptical imaging apparatus 12 and the illumination portion 14.

As illustrated in FIG. 10, a controller 18 of the optical inspectionapparatus 10 controls an image sensor 26 of the optical imagingapparatus 12, the illumination portion 14, and the conveyance portion16. States of the image sensor 26 of the optical imaging apparatus 12,the illumination portion 14, and the conveyance portion 16, and imagesacquired by the image sensor 26 of the optical imaging apparatus 12 canbe displayed on a display 9.

The optical imaging apparatus 12 according to the present embodiment hasa basic configuration similar to a basic configuration of the opticalimaging apparatus 12 according to the first embodiment. The opticalimaging apparatus 12 according to the present embodiment includes animage-forming optical portion 22 that has a first optical axis L1, awavelength selection portion 24, and the image sensor 26.

The conveyance portion 16 can convey a work (object) as an inspectionsubject not illustrated, by means of the conveyance path 16 a, in onedirection. A conveyance speed of a work by means of the conveyance path16 a of the conveyance portion 16 depends on a conveyance subject(inspection subject), and is, for example, approximately 7 m/s or less.

In the present embodiment, the wavelength selection portion 24 has alengthwise direction along a second axis Ay, and is divided into, forexample, five different regions in a direction along a first axis Ax.That is to say, in the present embodiment, the wavelength selectionportion 24 includes five different wavelength selection regions 24 a, 24b, 24 c, 24 d, and 24 e. The five different wavelength selection regions24 a, 24 b, 24 c, 24 d, and 24 e are a first wavelength selection region24 a, a second wavelength selection region 24 b, a third wavelengthselection region 24 c, a fourth wavelength selection region 24 d, and afifth wavelength selection region 24 e. Therefore, the number ofwavelength selection regions of the wavelength selection portion 24 thata first plane crosses is different from the number of wavelengthselection regions of the wavelength selection portion 24 that a secondplane crosses. Therefore, the wavelength selection portion 24 is ananisotropic wavelength selection opening that is non-isotropic oranisotropic, and has anisotropy. Note that here, it is assumed that thefirst wavelength selection region 24 a, for example, is disposed on thefirst optical axis L1 of the image-forming optical portion 22.

The image sensor 26 according to the present embodiment is a linearsensor. The image sensor 26 has a lengthwise direction along the secondaxis Ay, and pixels are linearly arranged along the lengthwisedirection. In the first plane where the first axis Ax and the firstoptical axis L1 extend, the image sensor 26 can be considered as apoint. In the present embodiment, five different wavelengths are used,and each pixel of the image sensor 26 receives five light beams ofdifferent combinations of the five different wavelengths by means ofseparate respective color channels, and identifies each of the lightbeams, based on a hue (component ratio of the color channels). Forexample, blue light of a wavelength of 450 nm is received by only acolor channel referred to as a B channel, green light of a wavelength of550 nm is received by only a color channel referred to as a G channel,and red light of a wavelength of 650 nm is received by only a colorchannel referred to as an R channel.

Note that in general, if the image sensor 26 includes three channels ofR, G, and B, the image sensor 26 can identify a difference betweenspectra (difference between hues), based on a component ratio of thethree channels of R, G, and B. Therefore, even if the number ofmulti-wavelength opening regions (wavelength selection regions) islarger than the number of image channels of the image sensor 26, theimage sensor 26 functions.

That is to say, in the present embodiment, each pixel of the imagesensor 26 includes three or more color channels. Based on an imageacquired by the image sensor 26, the controller 18 acquires informationabout scattering on an object surface, based on the number ofsignificant color channels (the number of color channels a pixel valueof each of which is equal to or larger than a value not buried by noiseor surrounding illumination).

The illumination portion 14 illuminates the conveyance path 16 a of awork, in the shape of a line that is long in a direction parallel to thesecond axis Ay. The illumination portion 14 illuminates a region R ofthe conveyance path 16 a, in the shape of a line, perpendicularly orsubstantially perpendicularly to a conveyance direction of theconveyance path 16 a. Illumination light of the illumination portion 14is, for example, white light, and is not single-color light.Alternatively, illumination light of the illumination portion 14 may bewhite light obtained by multiplexing single-color light. A shape ofillumination of the illumination portion 14 is not limited to the above,and may be anything. Further, the line-shaped illumination may actuallybe a rectangle that has a large aspect ratio. It is assumed that adirection along a lengthwise direction of the line-shaped illuminationis a fourth axis A4, and is parallel to the second axis Ay. It isassumed that a direction that is from the illumination portion 14 andperpendicularly crosses the fourth axis A4 is a second optical axis L2.Further, it is assumed that a direction that perpendicularly crossesboth the second optical axis L2 and the fourth axis A4 is a third axisA3.

It is assumed that a plane where the second optical axis L2 and thethird axis A3 extend is a third plane. It is assumed that the firstplane is parallel to the third plane. It is assumed that a plane wherethe second optical axis L2 and the fourth axis A4 extend is a fourthplane.

It is assumed that a light beam group emitted from the illuminationportion 14 is substantially parallel light in the third plane, and isdiffused light in the fourth plane.

Note that a position relationship between the illumination portion 14and the optical imaging apparatus 12 is set in such a manner that alight beam having the first wavelength that is in the third planeemitted from the illumination portion 14 and that regularly passes(regularly reflects) on a surface of a work (object surface) on theconveyance path 16 a illuminated with the light beam from theillumination portion 14, passes through the first wavelength selectionregion 24 a of the wavelength selection portion 24, and is incident onthe image sensor 26. That is to say, the illumination portion 14 and theimage sensor 26 are disposed in such a manner that a light beam thathaving the first wavelength that is in the third plane illuminated fromthe illumination portion 14, that regularly passes on an objectilluminated with the light beam from the illumination portion 14, thatpasses through the first wavelength selection portion 24, that isincident on the image sensor 26, and that is incident on the imagesensor 26, has object-side telecentricity at the image sensor 26.

Here, a light beam that is in the first plane and has telecentricity onthe object side of the image-forming optical portion 22 reaches thefirst wavelength selection region 24 a. In the present embodiment, thefirst wavelength selection region 24 a allows passing of a light beam ofthe first wavelength (blue light) through the first wavelength selectionregion 24 a, and shields light beams of a second wavelength (red light),a third wavelength (green light), and the other fourth wavelength andfifth wavelength. The second wavelength selection region 24 b allowspassing of a light beam of the second wavelength (red light) through thesecond wavelength selection region 24 b, and shields light beams of thefirst wavelength, the third wavelength, the fourth wavelength, and fifthwavelength. The third wavelength selection region 24 c allows passing ofa light beam of the third wavelength through the third wavelengthselection region 24 c, and shields light beams of the first wavelength,the second wavelength, the fourth wavelength, and the fifth wavelength.The fourth wavelength selection region 24 d allows passing of a lightbeam of the fourth wavelength and a light beam of the third wavelengthreceived by R channels of the image sensor 26 through the fourthwavelength selection region 24 d, and shields light beams of the firstwavelength, the second wavelength, and the fifth wavelength. The fifthwavelength selection region 24 e allows passing of a light beam of thefifth wavelength that is not received by any channel of the image sensor26 through the fifth wavelength selection region 24 e, and shields lightbeams of the first wavelength, the second wavelength, the thirdwavelength, and the fourth wavelength.

That is to say, a light beam that has passed through the firstwavelength selection region 24 a is received by B channels of the imagesensor 26. A light beam that has passed through the second wavelengthselection region 24 b is received by R channels of the image sensor 26.A light beam that has passed through the third wavelength selectionregion 24 c is received by G channels of the image sensor 26. Further,light beams that have passed through the fourth wavelength selectionregion 24 d are simultaneously received by the R channels and the Gchannels. A light beam that has passed through the fifth wavelengthselection region 24 e is not received by any channel.

It is assumed that a work that has a flat surface, for example, isconveyed. It is assumed that a surface of a work that includes a defect,a foreign matter, or ups and downs of the shape is an abnormal surface,and a surface of a work to the contrary is a standard surface. Thewavelength selection regions are formed in such a manner that when lightbeams from the illumination portion 14 are reflected by a standardsurface, the light beams pass through the first wavelength selectionregion 24 a of the wavelength selection portion 24.

Under the configuration described above, an operation principle of theoptical inspection apparatus 10 according to the present embodiment willbe described.

If a surface of a work is a standard surface, an image imaged by theimage sensor 26 as a linear sensor is B channels. That is to say, theimage sensor 26 images only light beams of the first wavelength (bluelight). Therefore, if the controller 18 determines that only light beamsof the first wavelength have been imaged when the controller 18determines a hue of an image acquired by the image sensor 26, thecontroller 18 determines that a surface of a work is a standard surface.That is to say, light beams that are emitted from the illuminationportion 14 and are in the third plane, receive regular passing from anilluminated object and are traveling to the image sensor 26, and reachthe wavelength selection portion 24 do not simultaneously pass throughtwo or more different wavelength selection regions.

On the other hand, if a work surface is an abnormal surface, a lightbeam direction reflected from the work changes compared with a case of astandard surface. That is to say, if the image sensor 26 as a linearsensor images any of light beams of the second wavelength (red light),the third wavelength (green light), the fourth wavelength, and the fifthwavelength in an imaged image, it can be said that a work surface is anabnormal surface. That is to say, light beams that are emitted from theillumination portion 14 and are in the third plane, do not receiveregular passing from an illuminated object and are traveling to theimage sensor 26, and reach the wavelength selection portion 24 passthrough any of the wavelength selection regions 24 b, 24 c, 24 d, and 24e. Further, light beams that are emitted from the illumination portion14 and are in the third plane, are diffused by an illuminated object andare traveling to the image sensor 26, and reach the wavelength selectionportion 24 simultaneously pass through two or more regions of thedifferent wavelength selection regions 24 a, 24 b, 24 c, 24 d, and 24 esince the light beams are diffused. Further, a component ratio of colorchannels of pixels of an imaged image changes according to a surfaceshape of a work. That is to say, the controller 18 can estimate asurface of a work, based on a value (pixel value) of each of colorchannels.

Further, the optical imaging apparatus 12 makes, for example, a table ofrelationships between surface shapes and combinations (component ratios)of pixel values of, for example, three color channels of R, G, and B,and stores the table in memory not illustrated. At this time, thecontroller 18 collates a component ratio of color channels of each pixelacquired by the image sensor 26 with the table stored in the memory, andthus can measure a surface shape of a surface of a work (objectsurface).

Especially if the controller 18 determines that two or more channels ofthree color channels of R, G, and B have been simultaneously imaged bythe image sensor 26, that is to say if the number of color channels thathave significant values is two or more, the controller 18 determinesthat a surface of a work is an abnormal surface, and light has beendiffused by the abnormal surface. On the other hand, a standard surfaceis imaged by one color channel of a light beam of the first wavelength(blue light). Therefore, the controller 18 of the optical inspectionapparatus 10 can estimate whether a surface of an object (objectsurface) is an abnormal surface or a standard surface, based on thenumber of significant color channels.

As described above, the optical inspection apparatus 10 according to thepresent embodiment can inspect a surface state of an object (work) thatis being conveyed, or can measure a surface shape of an object (work)that is being conveyed.

According to the present embodiment, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

In the present embodiment, an example is described where the opticalimaging apparatus 12 described in the first embodiment is used. Insteadof the optical imaging apparatus 12 described in the first embodiment,however, the optical imaging apparatus 12 described in the secondembodiment, or the optical imaging apparatus 12 described in the thirdembodiment may be used.

(Modification 1)

As illustrated in FIG. 11, an illumination portion 14 includes aplurality of linear illuminations 14 a, 14 b, and 14 c. Light-emittingdiodes (LEDs), for example, are used as light sources of the linearilluminations 14 a, 14 b, and 14 c. However, light sources of the linearilluminations 14 a, 14 b, and 14 c are not limited to LEDs and may belasers of some multiplexed different wavelengths. For example, lasers ofwavelengths of 405 nm, 532 nm, and 635 nm are multiplexed using a coldmirror, a hot mirror, or the like to form illumination light. At leasttwo or more of the linear illuminations 14 a, 14 b, and 14 c of theillumination portion 14 may be included.

FIG. 11 is a cross-sectional view that includes a first optical axis L1and second optical axes L2 a, L2 b, and L2 c of light beams from thelinear illuminations 14 a, 14 b, and 14 c. The first linear illumination14 a, the second linear illumination 14 b, and the third linearillumination 14 c illuminate a region R of a conveyance path 16 a, eachin the shape of a line, perpendicularly to a conveyance direction of theconveyance path 16 a. Regions (illuminated portions) R illuminated bythe first linear illumination 14 a, the second linear illumination 14 b,and the third linear illumination 14 c are superimposed on each other.In the present modification, a controller 18 controls the linearilluminations 14 a, 14 b, and 14 c to simultaneously illuminate asuperimposed region R of a surface of a work W (object surface). Withrespect to light beams illuminated by each of the linear illuminations14 a, 14 b, and 14 c and reflected by a surface of the work W, part ofthe light beams projected on a cross section illustrated in FIG. 11become parallel light relative to an image-forming optical portion 22 ofan optical imaging apparatus 12. Among light beams from the linearilluminations 14 a, 14 b, and 14 c of the illumination portion 14, partof the light beams that receive regular reflection (regular passing)from a surface of the work W become parallel light parallel to a firstplane and a second plane. With respect to light beams illuminated byeach of the linear illuminations 14 a, 14 b, and 14 c and reflected bythe work W, part of the light beams projected on a plane thatperpendicularly crosses a cross section illustrated in FIG. 11 becomediffused light relative to the image-forming optical portion 22 of theoptical imaging apparatus 12.

If a standard surface of a work W is a mirror surface, light beams withwhich the work W is illuminated become regular reflection. At this time,reflection directions of the second optical axes L2 a, L2 b, and L2 c ofthe light beams change according to the shape of the work W. Therefore,a hue of an image acquired by an image sensor 26 of the optical imagingapparatus 12 changes according to a change in the shape based onmovement of the work W by a conveyance path 16 a. Based on such a changein the hue, the controller 18 of the optical imaging apparatus 12 of anoptical inspection apparatus 10 can estimate the shape of a surface ofthe work W.

If there is a foreign matter F or minute protrusions and recesses ofscales close to a wavelength of light on a surface, light beams from theillumination portion 14 are scattered. That is to say, light beams fromthe first linear illumination 14 a, the second linear illumination 14 b,and the third linear illumination 14 c are diffused and reflected by theforeign matter F. The number of wavelength selection regions of awavelength selection portion 24 through which the diffused light beamspass increases compared with a case where light beams are reflected by astandard surface. Therefore, the number of significant color channels ofthe image sensor 26 increases. That is to say, in an image acquired bythe image sensor 26 of the optical imaging apparatus 12, the number ofsignificant color channels increases in an abnormal-surface region wherethere is a foreign matter F, minute protrusions and recesses, or thelike. Based on such an increase in the number of significant colorchannels, the controller 18 of the optical inspection apparatus 10 caninspect a surface of a work W.

Therefore, due to the optical inspection apparatus 10 according to thepresent modification, a surface of a work can be inspected using theoptical imaging apparatus 12 even if the surface of the work has acurved surface.

According to the present modification, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

(Modification 2)

An illumination portion 14 may include a configuration illustrated inFIG. 12. FIG. 12 is a cross section that includes a first optical axisL1 and a second optical axis L2. The illumination portion 14 includes alight source 114, a concave mirror 116, and a beam splitter 118. It isassumed that the light source 114 is, for example, an LED light sourceof white color (no single color). It is assumed that the concave mirror116 is, for example, an elliptical mirror.

In the present modification, an optical imaging apparatus 12 isdisposed, for example, above the beam splitter 118 of the illuminationportion 14 in FIG. 12. In the present modification, the second opticalaxis L2 of the illumination portion 14 and the first optical axis L1 ofthe optical imaging apparatus 12 are made parallel by means of the beamsplitter 118. That is to say, part of light beams emitted from the lightsource 114 are made to become parallel light parallel to the firstoptical axis L1, using the concave mirror 116 and the beam splitter 118.Illumination made parallel to the optical axis L1 of imaging in this wayis referred to as coaxial epi-illumination. The illumination iscondensed light in, for example, the cross section illustrated in FIG.12. On the other hand, the illumination is diffused light in a planethat perpendicularly crosses the cross section.

An image acquired by an image sensor 26 of an optical imaging apparatus12 has different hues according to a change in a shape of an object (notillustrated). Based on such a change in the hue, the controller 18 of anoptical inspection apparatus 10 can estimate a shape of a surface of awork (object surface). Further, in an image acquired by the opticalimaging apparatus 12, the number of significant color channels increasesin an abnormal-surface region where there is a foreign matter F, minuteprotrusions and recesses, or the like. Based on such an increase in thenumber of significant color channels, a surface of a work W can beinspected.

According to the present modification, the optical imaging apparatus 12,the optical inspection apparatus 10, and the optical inspection methodfor acquiring information about an object surface can be provided.

According to at least one of the embodiments described above, theoptical imaging apparatuses 12, the optical inspection apparatuses 10,and the optical inspection methods for acquiring information about anobject surface can be provided.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An optical imaging apparatus comprising: animage-forming optical portion that forms an image of an object by meansof light beams that include a first wavelength and a second wavelengthdifferent from the first wavelength, the image-forming optical portiondefining a first axis that intersects a first optical axis of theimage-forming optical portion, and defining a second axis thatintersects the first optical axis of the image-forming optical portionand the first axis; a first wavelength selection portion havingwavelength selection regions, the wavelength selection regions being ananisotropic wavelength selection opening having a different distributionof the wavelength selection regions depending on a direction along thefirst axis and a direction along the second axis, a first light beamhaving the first wavelength, the first light beam having object-sidetelecentricity in an axis direction of the first axis of theimage-forming optical portion and having object-side non-telecentricityin an axis direction of the second axis, a second light beam having thesecond wavelength, the second light beam having object-sidenon-telecentricity in the axis direction of the first axis and the axisdirection of the second axis, the first wavelength selection portionsimultaneously allowing passing of the first light beam and the secondlight beam; and an imaging portion that is configured to simultaneouslyacquire an image of the first light beam and the second light beam. 2.The optical imaging apparatus according to claim 1, wherein thewavelength selection regions of the first wavelength selection portionincludes: a first wavelength selection region which is disposed in afocal plane of the image-forming optical portion; and a secondwavelength selection region which is aligned offset with the firstwavelength selection region in the axis direction of the first axis,when it is assumed that a plane where the first optical axis and thefirst axis extend is a first plane, and a plane where the first opticalaxis and the second axis extend is a second plane, among light beamsfrom the object to the imaging portion, in the first plane, a light beamthat reaches the first wavelength selection region has object-sidetelecentricity, a light beam that reaches the second wavelengthselection region has object-side non-telecentricity, and in the secondplane, a light beam that reaches the first wavelength selection regionthat is away from the first optical axis has object-sidenon-telecentricity.
 3. The optical imaging apparatus according to claim1, comprising a controller that is configured to acquire a direction ofa light beam relative to the first axis, based on a hue acquired by theimaging portion.
 4. The optical imaging apparatus according to claim 3,wherein each pixel of the imaging portion includes two or more colorchannels, and the controller is configured to acquire information aboutscattering on an object surface, based on a number of the color channelssignificant in the controller.
 5. The optical imaging apparatusaccording to claim 1, wherein the imaging portion is a linear sensor inwhich pixels are linearly disposed.
 6. The optical imaging apparatusaccording claim 5, wherein when it is assumed that a plane where thefirst optical axis and the first axis extend is a first plane, and aplane where the first optical axis and the second axis extend is asecond plane, the linear sensor has a lengthwise direction in adirection parallel to the second plane.
 7. The optical imaging apparatusaccording to claim 1, comprising: a polarizing beam splitter that isdisposed between the image-forming optical portion and the firstwavelength selection portion and splits a polarized-light component intoa first polarized-light component and a second polarized-lightcomponent; and a second wavelength selection portion disposed on a lightpath of a light beam split by the polarizing beam splitter, wherein: afirst polarized-light component is made to be incident on the firstwavelength selection portion, and a second polarized-light componentdifferent from the first polarized-light component is made to beincident on the second wavelength selection portion.
 8. The opticalimaging apparatus according to claim 1, wherein the first wavelengthselection portion is disposed between the image-forming optical portionand the imaging portion.
 9. The optical imaging apparatus according toclaim 1, wherein the first wavelength selection portion is disposedcloser to the object as an inspection subject than the image-formingoptical portion is disposed.
 10. An optical inspection apparatuscomprising: the optical imaging apparatus according to claim 1; and anillumination portion that illuminates the object with light beams thatinclude the first wavelength and the second wavelength.
 11. The opticalinspection apparatus according to claim 10, wherein the illuminationportion includes a second optical axis, and when it is assumed that adirection that crosses the second optical axis is a third axis, adirection that crosses the second optical axis and the third axis is afourth axis, a plane where the second optical axis and the third axisextend is a third plane, and a plane where the second optical axis andthe fourth axis extend is a fourth plane, light beams emitted from theillumination portion are substantially parallel light in the third planeand are diffused light in the fourth plane.
 12. The optical inspectionapparatus according to claim 11, wherein the first wavelength selectionportion includes: a first wavelength selection region that allowspassing of the first light beam through the first wavelength selectionregion and shields the second light beam; and a second wavelengthselection region that is aligned offset with the first wavelengthselection region in the axis direction of the first axis, shields thefirst light beam, and allows passing of the second light beam throughthe second wavelength selection region, and a position relationshipbetween the illumination portion and the imaging portion is set in sucha manner that a light beam having the first wavelength that is in thethird plane illuminated from the illumination portion and that regularlypasses on an object surface illuminated with the light beam from theillumination portion, passes through the first wavelength selectionregion, and is incident on the imaging portion of the wavelengthselection portion, and is incident on the imaging portion.
 13. Theoptical inspection apparatus according to claim 11, wherein a positionrelationship between the illumination portion and the imaging portion isset in such a manner that a light beam having the first wavelength thatis emitted from the illumination portion that is in the third planeilluminated from the illumination portion, that regularly passes on anobject surface illuminated with the light beam from the illuminationportion, that passes through the first wavelength selection portion,that is incident on the imaging portion, and that is incident on theimaging portion, has object-side telecentricity at the imaging portion.14. The optical inspection apparatus according to claim 11, wherein alight beam that is in the third plane illuminated from the illuminationportion that regularly passes from the object illuminated, that reachesthe first wavelength selection portion, and that travels to the imagingportion, do not simultaneously pass through two or more differentwavelength selection regions.
 15. The optical inspection apparatusaccording to claim 10, comprising at least two or more of theillumination portion, wherein: when it is assumed that a plane where thefirst optical axis and the first axis extend is a first plane, and aplane where the first optical axis and the second axis extend is asecond plane, among light beams from the illumination portion, part ofthe light beams that receive regular passing from the object becomeparallel light parallel to the first plane and the second plane.
 16. Theoptical inspection apparatus according to claim 10, comprising acontroller that is configured to image a surface of the objectilluminated by the illumination portion, by means of the imaging portionto acquire an image, and configured to inspect a surface state of theobject or measures a surface shape of the object.
 17. An opticalinspection apparatus comprising: the optical imaging apparatus accordingto claim 1; a conveyance portion that is configured to convey the objectin a predetermined direction; and a controller that is configured toimage a surface of the object that is being conveyed, by means of theimaging portion to acquire an image, and configured to inspect a surfacestate of the object or measures a surface shape of the object.
 18. Anoptical inspection apparatus according to claim 17, comprising anillumination portion that is configured to illuminate the object withlight beams that include the first wavelength and the second wavelength.19. An optical inspection method comprising: imaging a first light beamthat has a first wavelength and a second light beam that has a secondwavelength different from the first wavelength at an imaging portion, bymeans of an image-forming optical portion passing through theimage-forming optical portion and a wavelength selection portion from anobject; and simultaneously acquiring an image of the first light beampassed through the wavelength selection portion and an image of thesecond light beam passed through the wavelength selection portion bymeans of the imaging portion, the first beam having object-sidetelecentricity in an axis direction of a first axis that crosses a firstoptical axis of the image-forming optical portion and having object-sidenon-telecentricity in an axis direction of a second axis that crossesthe first optical axis and the first axis, and the second light beamhaving object-side non-telecentricity in the axis direction of the firstaxis and the axis direction of the second axis.
 20. An opticalinspection method comprising: incident of a first light beam having afirst wavelength and a second light beam having a second wavelengthdifferent from the first wavelength on an object; simultaneously passingthe first light beam and the second light beam through a wavelengthselection portion, the first light beam having object-sidetelecentricity in the axis direction of the first axis that crosses thefirst optical axis of an image-forming optical portion and hasobject-side non-telecentricity in the axis direction of the second axisthat crosses the first optical axis and the first axis, and the secondlight beam having object-side non-telecentricity in the axis directionof the first axis and the axis direction of the second axis; formingimages of the first light beam and the second light beam that have beenallowed to pass through the wavelength selection portion by means of theimage-forming optical portion; and acquiring the images of the firstlight beam and the second light beam that have been allowed to passthrough the wavelength selection portion by means of an imaging portion.